Iron

ABSTRACT

The invention relates to an electrical iron. An iron comprises a sole plate, of a glass or ceramic substrate bearing an electrical heating element. The electrical heating element comprises a transparent or translucent antimony tin oxide thin film which directly heats the glass or ceramic substrate.

FIELD OF THE INVENTION

The present invention relates to electrical irons.

BACKGROUND TO THE INVENTION

Domestic irons consists of a heated metal sole plate onto which waterfrom a reservoir is dripped to generate steam, which is then emittedthrough holes in the sole plate. The clothes are then pressed by anaction of heat and steam. This method produces a small and varyingamount of steam and is really only suitable for small amounts ofclothes.

An improvement has been made through the introduction of separate waterreservoir and steam generators. In this embodiment, a water tank andsteam generator is separate from the iron, which also consists of aheated sole plate.

The generated steam is then sent down a pipe to the iron, where aconstant stream of steam is then released onto the clothes. This methodhas the advantage of a large water tank for heavy use and a constantflow of steam. The main disadvantage is that the steam can cool down inthe pipe and the system is very inefficient and takes a long time towarm up.

With the latter system, one option would be to pump water up a pipe andgenerate steam in the iron. However, current nichrome heating technologyhas a power density limitation, because if the heater becomes too hot,then it will oxidize or burn out. Thus without making the iron muchlarger and having a dramatic impact on the sole plate temperature, thevolume of steam generation is limited. Making the heater separate fromthe iron allows for a large heater sub-assembly and hence a large rateof steam without the requirement for a large heater power density at theexpense of heat up time and efficiency. A further disadvantage of thismethod is that the steam has to be re-heated at the iron and this canimpact on the sole plate temperature at higher flow rates initially whenthe iron is cold, until the iron is at the correct working temperature.In particular, if a sole plate with poor thermal conductivity is used,then this will become a potentially large problem.

We have therefore appreciated the need for an improved iron and steamgeneration system.

SUMMARY OF THE INVENTION

According to a first aspect, there is provided an iron comprising a soleplate, the sole plate comprising a glass substrate bearing an electricalheating element. In preferred embodiments, said heating elementcomprises a substantially transparent film coating of conducting orsemi-conducting material.

Preferably, said film coating comprises a semi-conducting oxide, moreparticularly a doped tin oxide, for example antimony tin oxide(Sb₃O₄/SnO₂), fluorine-doped tin oxide or some other substantiallytransparent conducting doped oxide material. Thus although the use ofantimony tin oxide (ATO) film coatings has been found to be especiallyadvantageous due to temperature stability, embodiments of the inventionalso contemplate substitution of an ATO film coating by a film of adifferent, electrically conducting material, for example, an alternativesubstantially transparent conducting oxide film, preferably a tin oxidefilm, for example Indium Tin Oxide, or a mixture of doped oxides.

Use of a high thermal conductivity material or substrate for the tubesfacilitates a relatively low temperature for the heated ATO films, forexample less than 200° C.

In embodiments the ATO film coatings are substantially covalently bondedto their substrates, which reduces the risk of lift-off or delaminationfrom the substrate. This can be achieved by cleaning and passivation ofthe substrate surfaces on which the ATO coatings are deposited.

In embodiments the ATO film coatings are substantially transparent andin combination with a transparent substrate, such as glass, this enablesthe fabrication of an iron through which clothes being ironed arevisible during ironing. This can provide benefits in that such anarrangement facilitates monitoring of the clothes being ironed such thatcreases to be ironed out are more easily seen by the user.

The use of an antimony tin oxide film also provides other advantagessince, in embodiments, such films are scratch resistant, oxidationresistant, substantially chemically inert.

In preferred embodiments, the iron comprises a secondary layer of glassor ceramic laminated over said glass substrate with a gap there between.The secondary glass layer over the glass substrate provides a thermaland electrical insulation barrier from the glass substrate.

There is also provided a layer of transparent polymer disposed over saidsecondary layer of glass, such that a gap is formed between saidtransparent polymer and said secondary glass layer for thermallyinsulating the transparent polymer from the glass substrate.

This structure enables the clothes to remain visible to the user evenduring ironing, whilst insulating the user from the heat of the heatedglass sole of the iron. The gap between the glass substrate and thesecondary layer may be filled with an inert gas, for example krypton,for additional insulation.

However, in other embodiments the secondary glass or ceramic layerand/or the upper polymer layer may be opaque, in which case the userwould not be able to see through those layers to the material underneaththe sole plate in use.

In embodiments, the iron comprises a hub for attaching said sole plateto a handle, wherein the electrical connections from the power supply,and switches/controls to the heating element which are in the handle arerouted through said hub. The outer casing of hub itself is electricallyisolated from the internal electrical connections, so as to avoid riskof electric shock to the user. Preferably, the hub comprises one or moreconduits for guiding steam to a surface of said sole plate.

In another embodiment, there is provided an iron having a vapour outletpositioned at a front of the iron, which emits water vapour or mist ontoa region immediately in front of the tip of the sole plate, or throughthe sole plate face.

In preferred embodiments, the glass substrate of the iron is patternedwith electrically and thermally conducting power rails in the form ofmetal tracks, for providing additional, localised, heating of said glasssubstrate. Preferably, the metal is silver.

In an embodiment of the iron, the power rails are formed of stripesalong a substantial length of each of the longer edges of said glasssubstrate and one or more stripes along a substantial length of acentral region of said glass substrate.

In an alternative embodiment, said power rails are formed of a rearportion disposed at a trailing end of said glass substrate, and aforward portion disposed at a leading end of said glass substrate, saidrear portion covering substantially the width of the glass substrate andtapering towards the outer edges of the glass substrate, and saidforward portion comprising one or more triangular portions and abridging portion, said bridging portion covering a stripe acrosssubstantially the width of said glass substrate.

In a further alternative embodiment, said power rails are formed of edgeportions along the long edges of said glass substrate, and wherein aforward portion of said edge portions located at a leading end of saidglass substrate has a greater width than said edge portions along theremaining edge portion.

In yet a further embodiment, there may be provided a metal or metaloxide layer formed as an area over the sole plate between two edges ofthe sole plate. In this embodiment, there may be at least a pair ofoppositely facing power rails, positioned one on each side of the soleplate, and extending between said pair of power rails, a continuous areaof thin film metal oxide heating element. The thin film metal oxideheating element may extend across almost the full width of the soleplate, and may extend substantially along the whole length of the soleplate. Alternatively, a small number of separate areas of thin film,each independently controlled and each extending across a full width ofthe sole plate may be provided.

The shape of the sole plate need not be a conventional arched or bulletshaped sole plate area, but in other embodiments, elliptical, ovoid orother geometric shapes for the sole plate footprint may be formed. Theshape of the sole plate footprint may influence whether the metal oxideheating element formed as a series of individual elements, or as asingle film extending across the whole of the sole plate, or as aplurality of areas of film heating element extending across the soleplate.

In an embodiment of the iron, the electrical heating element ispatterned to maintain a substantially constant heat profile across saidglass substrate. This provides a substantially constant level of heatacross the glass substrate, which leads to a substantially constantpower rating.

Preferably, the pattern of said electrical heating element comprises aplurality of heating element tracks, and wherein each of said heatingelement track has substantially the same length.

Preferably, the glass substrate is patterned with first and secondelectrically conducting power rails for providing power to said heatingelements, and wherein each of said heating elements is electricallyconnected between said first and second power rails. In this embodiment,the first power rail runs substantially along a central portion of thelength of said glass sole plate and said second power rail runssubstantially along one or more edges of said glass substrate.Preferably, the pattern of said heating elements comprises one or moreturns in direction such that the heating element tracks follow a zig-zagor serpentine path between said first and second power rails.

In embodiments, the sole substrate bears a layer of semiconductingmaterial, wherein said heating element is formed from saidsemiconducting material, and wherein said iron includes a temperaturesensor comprising a portion of said layer of semiconducting material.

In some preferred embodiments the film coating comprises a semiconducting material and a switch for the heating element is fabricatedwithin part of a layer of the same material (either within the heatingelement itself or as a separate device, for example patterned in acommon layer of semiconducting material.

In some preferred embodiments, the iron comprises a steam generator forgenerating steam for applying to said sole plate, said steam generatorcomprising: a first tube; a second tube located within a bore of saidfirst tube to define a first space between an inner wall of said firsttube and an outer wall of said second tube, said second tube beingcoupled to a water input and having a plurality of conduits forcommunicating input water to said first space; a steam output coupled tosaid first space for expelling generated steam; a film coating of dopedtin oxide on an outer wall of said first tube; and electronicconnections to said film coating to enable electricity to be passedthrough said film coating to thereby heat water flowing through saidfirst space to generate steam.

The term “tube” is not intended to be restricted to a circularcross-section. In embodiments, the tube cross-section may instead beelliptical, oval, rectangular, square, triangular, polygonal and thelike.

In embodiments, the film coating comprises ATO (antimony tin oxide).Preferably, the first tube comprises a glass substrate. Alternatively,the first tube comprises a ceramic substrate.

In embodiments, the second tube comprises a first sub-tube locatedwithin the bore of a second sub-tube to define a second space between anouter wall of said first sub-tube and an inner wall of said secondsub-tube, and wherein said first and second sub-tubes comprise aplurality of conduits for communicating input water to said first andsecond spaces. Preferably, the first and second sub-tubes are rotatablerelative to one another about an axial axis of said tubes.

In embodiments, the film coating of the steam generator includes atemperature sensor comprising a portion of said film coating.

In some embodiments, the said steam generator further comprises: anelectrical power input; and an electrical power control deviceelectronically connected between said electrical power input and saidfilm coating; wherein said electrical power control device is asemiconductor device; and wherein at least a portion of saidsemiconductor device comprises a portion of said film coating.

In embodiments, the steam generator comprises a non-return or one-wayvalve between the second tube and the water input to prevent waterreturning to the input. Preferably, the steam generator comprises apriming mechanism for providing an initial amount of water to the steamgenerator. Alternatively, the steam generator comprises a pump forproviding water to the steam generator. Preferably the pump is amechanical, electrical or heat pump.

The steam generator may form part of the iron, or may be separate fromthe iron. In embodiments where the steam generator is separate from theiron, the steam generator is connected to the iron by means of aconnecting tube.

In embodiments the electrical heating element, in particular where itcomprises a thin film, for example a layer of semiconducting material,may itself be used as a temperature sensor. In this case a signal maybemodulated onto the electrical power, typically DC or low-frequency AC,supplying the heating element, to enable this signal to be detected bydemodulation. For example a higher frequency AC signal than a frequencyof an AC current providing power for heating the heating element may beemployed. Additionally or alternatively a region of the film maybedefined to be dedicated to temperature sensing and being provided withat least one separate electrode connection (optionally sharing oneelectrode connection with the heating element).

In an iron as described above an electrical power control device orswitch maybe incorporated into a layer semiconducting material formingthe heating element itself. For example by applying a gate electrodeover an insulating layer on a portion of the semiconducting layer an FET(Field Effect Transistor) switch may be fabricated. Such a device may befabricated in a dedicated, separately defined region of thesemiconducting layer or may be incorporated into the heating element,for example extending along the length of an electrode connection to theheating element.

Thus in a further aspect an iron comprises: an electrical power input;an electrical heating element, and an electrical power control deviceelectronically connected between said electrical power input and saidelectrical heating element; whereas said electrical heating elementcomprises a layer of semiconducting material on a substrate; whereinsaid electrical power control device is a semiconductor device; andwherein at least a portion of said semiconductor device comprises aportion of said layer of semiconducting material.

In embodiments the portion of the layer of semiconducting materialcomprising the electrical power control device is connected in seriesthe material defining the electrical heating element, and in embodimentsthe semiconductor device and heating element may be part of the same,substantially continuous layer of semiconducting material (rather thanneeding to be defined in a separate, dedicated region of thesemiconducting layer).

The device may comprise a diode, in particular a diode using ametal-semiconductor junction. Alternatively p-type and n-type dopedregions of the layer maybe employed to fabricate a bipolar transistor.Alternatively, as previously described, an insulated gate FET (orjunction FET) maybe fabricated. In general the power controlledsemiconductive device comprises an FET, bipolar transistor, IGBT,thyristor, SCR rectifier, TRIAC, or other device. In embodiments thedevice and heating element and substrate may be substantiallytransparent.

Suitable materials include, but are not limited to, tin oxide, forexample doped with antimony or fluorine, indium tin oxide, and siliconcarbide.

In a second aspect there is provided a method of controlling electricalpower to the electrical heating element of an iron comprising a layer ofsemiconducting material, the method comprising forming a semiconductordevice in said semiconducting material comprising said heating elementto control said electrical power.

Embodiments include a steam generator for generating steam said steamgenerator comprising:

a first tube;

a second tube located within said first tube to define a first spacebetween an inner wall of said first tube and an outer wall of saidsecond tube, said second tube being coupled to a water input and havinga plurality of conduits for communicating input water to said firstspace;

a steam output coupled to said first space for venting generated steam;

a film coating of doped tin oxide on an outer wall of a said tube; and

electrical connections to said film coating to enable electricity to bepassed through said film coating to thereby heat water flowing throughsaid first space to generate steam.

The steam generator can be located in the hand iron itself, or in asteam station which supplies steam to an iron. Where the steam stationsupplies steam to an iron having a glass or ceramic soleplate, the ironmay have a further such steam generator used to reheat the steam at theiron.

Another embodiment comprises an iron comprising:

a glass or ceramic sole plate; and

a semi-conductor heating element formed directly on said glass orceramic sole plate;

wherein said heating element is formed in a substantially serpentinepath.

According to a further embodiment, there is provided an iron comprising:

a substantially transparent or translucent glass or ceramic sole plate;

a substantially transparent semi-conductor film heating element formedon said glass or ceramic sole plate;

a secondary glass or ceramic layer positioned adjacent and spaced apartfrom said substantially transparent film heating element; and

a further transparent cover layer positioned over and spaced apart fromsaid secondary layer, such that a heat insulating gap is formed betweensaid cover layer and said secondary layer for thermal insulating saidcover layer from said sole plate.

According to yet a further embodiment, there is provided an ironcomprising:

a glass or ceramic sole plate;

a plurality of heating elements formed on said glass or ceramic soleplate;

wherein said plurality of heating elements are arranged into a firstregion, in which a said heating element has a first power dissipation;and

a second area in which a said heating element has a second powerdissipation,

wherein said first power dissipation is higher than said second powerdissipation.

Said first, higher power dissipation area is positioned at or in aregion of a tip of said sole plate.

The embodiments include an iron comprising:

a glass or ceramic sole plate;

a semi-conductor thin film heating element formed directly on said soleplate; and

a semi-conductor thin film fuse element formed directly on said soleplate, and connected in series with said heating element,

said fuse arranged to terminate a current flow when a current taken bysaid heating element exceeds a pre-determined threshold current.

In other embodiments, there may be provided a semiconductor thin filmheating element with no semiconductor thin film fuse, but with amechanical fuse in series with the thin film heating element. In yetother embodiments there may be provided a mechanical fuse in series witha semiconductor thin film fuse on the direct power to the heatingelement to provide additional safety.

The embodiments includes an iron comprising:

a glass or ceramic sole plate; and

a semi-conductor thin film heating element formed on said glass orceramic sole plate;

wherein said heating element comprises a plurality of tracks ofsemi-conductor thin film extending between a first power rail positionedon a first side of said sole plate and a second power rail position on asecond side of said sole plate,

wherein said plurality of tracks are arranged such as to provide asubstantially uniform power dissipation across substantially a wholearea of said sole plate.

Each of said plurality of heating elements may extend between said afirst and second sides of said sole plate; and

each said heating element extends from said first and second powerrails, towards a tip of said sole plate.

Other aspects are as recited in the claims herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and to show how the same maybe carried into effect, there will now be described by way of exampleonly, specific embodiments, methods and processes according to thepresent invention with reference to the accompanying drawings in which:

FIG. 1 shows an embodiment iron according to a first specific embodimentof the invention;

FIG. 2 shows a side view of the iron of FIG. 1;

FIGS. 3 a to 3 c show embodiment irons with different patterns of powerrail on the sole plate;

FIG. 3 a shows in view from underneath a second iron according to asecond specific embodiment, having a transparent or semi-transparentglass or ceramic sole plate having a first heating element track layout;

FIG. 3 b illustrates schematically in view from underneath a third ironhaving a transparent or semi-transparent glass or ceramic sole platehaving a second heating element track layout;

FIG. 3 c illustrates schematically in view from underneath a fourth ironhaving a transparent or semi-transparent glass or ceramic sole platehaving a third heating element track layout;

FIG. 3 d illustrates schematically in view from underneath fifth ironhaving a transparent or semi-transparent glass or ceramic sole platehaving a fourth heating element track layout, having a relatively higherpower output at the tip of the sole plate compared to the main body ofthe sole plate;

FIG. 4 shows a sixth embodiment iron with an alternative pattern ofheating element and power rail on the sole plate;

FIG. 5 shows a cross section through a steam generator according to aseventh specific embodiment disclosed herein;

FIG. 6 shows a distribution of current across a sole plate having auniformly coated thin film heating element, showing build up of hotspots;

FIG. 7 illustrates schematically one possible approach to reducing thehot spots on the iron sole plate shown in FIG. 6 herein;

FIG. 8 illustrates schematically a graph of sheet resistance againstwidth for the sole plate as shown in FIG. 7 herein;

FIG. 9 illustrates schematically a second approach to reducing the buildup of hot spots on the iron sole plate of FIG. 6 herein;

FIG. 10 illustrates schematically a plot of heated area fraction againstwidth for the heating elements as shown in FIG. 9 herein;

FIG. 11 illustrates schematically a seventh iron according to an eighthspecific embodiment, having a sole plate patterned with thin filmheating elements to achieve a substantially uniform power density;

FIG. 12 illustrates schematically a one time thermal fuse formed from athin film coating according to a ninth specific embodiment;

FIG. 13 illustrates schematically in perspective view an eighth ironaccording a tenth specific embodiment herein;

FIG. 14 illustrates schematically in view from above, the eighth iron asshown in FIG. 13 herein; and

FIG. 15 herein illustrates schematically in cross sectional view a glasssole plate having a recessed glass plate surrounded by an aluminiumouter rim or frame;

FIG. 16 herein illustrates in view form underneath a metal rimmed glasssole plate; and

FIG. 17 herein shows in cross sectional view an embodiment of layers ofa glass sole plate iron.

DETAILED DESCRIPTION

There will now be described by way of example a specific modecontemplated by the inventors. In the following description numerousspecific details are set forth in order to provide a thoroughunderstanding. It will be apparent however, to one skilled in the art,that the present invention may be practiced without limitation to thesespecific details. In other instances, well known methods and structureshave not been described in detail so as not to unnecessarily obscure thedescription.

In specific embodiments disclosed herein, there is provided an ironhaving a glass or ceramic sole plate, which is heated directly by a thinfilm semi-conductor material, for example an antimony tin oxide coating,or an equivalent semi-conductor coating, for example doped indium tinoxide (ITO) or doped fluorine tin oxide (FTO).

In this specification, where the term antimony tin oxide is used, thisencompasses materials including antimony oxide and tin oxide, andincluding materials with the chemical formula Sb₃O₄*SnO₂, as well asmaterials with the formula Sb₂O₃*SnO₂, including such compounds whichare doped with donor or acceptor materials so as to affect theresistivity or conductivity of the antimony tin oxide material. Thematerial may be formed on a glass or ceramic substrate by sputtering,evaporation, chemical vapor deposition (CVD), or by other knownprocesses for forming or depositing a semi-conductor layer on to a glassor ceramic substrate.

In this specification, where the term “heating element” is used, thisgenerally describes a doped metal oxide film through which electricityis passed to generate heat. The heating elements may be divided intoelongate straight, curved or meandering tracks, or may be formed asareas of different geometric shapes.

Where the term “power rail” is used, this generally refers to a metalstrip, track, film or coating used to supply power to one or moreheating elements.

The Iron makes use of clear thin film resistive coating (e.g. ATO) on aglass substrate as the heating element to provide the mechanism forheating a sole plate to facilitate crease removal from fabrics.

Iron with Central Hub

Referring to FIGS. 1 and 2 herein, an iron comprises a glass sole plate(1); an upper transparent portion (2); a handle (4) attached to theupper transparent handle; and a hub (3) connecting the sole plate to thehandle.

Steam is delivered to the garment being ironed through the hub (3),which also forms the fixing point for the glass panels and electricalcontact to the film coating on the glass sole.

The sole plate assembly is thermally and electrically insulated from thehandle assembly (4) by a combination of a secondary glass sheet (8)laminated over the ATO coating (dotted line 10), an air gap (potentialto fill with inert gas, such as krypton, for extra insulation) and atransparent moulded polymer (7).

In the iron of FIGS. 1 and 2, a steam generator as described withreference to FIG. 5 herein may be incorporated within the handle of theiron, as a tubular heating element, so that water may flow from a basereservoir unit through a feed tube connecting the base unit to the handiron, and passes through the tubular heating element within the handleso as to be ejected as steam or heated spray at the sole plate. Water isheated continuously, as it flows through the inline tubular heatingelement contained within the handle.

In FIG. 2, the laminated construction of the first iron is shown incross sectional view. The layers include a glass or ceramic plate (9)which forms a main structural body of the sole plate; formed directly ontop of the glass sole plate, a thin film heating element coating forexample an ATO coating; on top of the ATO coating, secondary transparentglass or ceramic sheet (8), which is in direct contact with and bondedto the sole plate (9) and the ATO coating (10); above the soleplate/secondary plate laminate (8, 9, 10) is provided an upper casing(7) which may be ceramic, or of a moulded transparent polymer orplastics material. Between the transparent casing (7) and the secondarysheet (8) is a void cavity (11), the purpose of which is to providethermal insulation from the secondary glass sheet (8) which may heat upto a temperature similar to that of the glass sole plate (9). The uppertransparent casing (7) prevents a user from burning themselves on theunderlying sole plate and secondary glass or ceramic plate (8) andprovides an acceptable touch temperature, whilst its transparentproperties allows the user to see through the casing, secondary glasssheet and sole plate to see the fabric underneath the sole plate as itis being ironed and pressed.

Key benefits have been identified when using thin film technology asheating mechanism, these include:

-   -   Visibility through to the fabric to be ironed (avoiding ironing        in creases and for navigation around garment fixings (zips,        buttons etc)).    -   Improved manoeuvrability due to the surface quality of the glass        (minimal drag) and lightweight assembly.

Zonal Heating

Referring to FIGS. 3 a to 3 c herein, the ATO coating (12) and printedsilver tracking (11) can be configured to optimise the base plateefficiency and bring intelligence in zonal heating to the soleplate fordifferent ironing tasks.

The structure of FIG. 3 a, this pattern will create an even horseshoeband of heat on the soleplate.

The structure of FIG. 3 b will create a consistent even heat to the mainplate and allow the front tip to be tweaked for ‘intense’ heat ifrequired to iron out stubborn creases.

The structure of FIG. 3 c will create a graduated heat profile to themain plate (hotter towards front) and allow the front tip to be tweakedfor ‘intense’ heat if required.

Key benefits have been identified when using thin film technology asheating mechanism, these include energy savings due to ‘heat zoning’,when the electrodes can be designed to be switchable and allow shut offor pulsing of particular areas of the heating surface. This helps withcost savings in the Bills of Materials (BOM) and manufacturing process.

Referring to FIG. 3 d herein, there is illustrated schematically a fifthiron sole plate having a zoning of heating elements so as to provide arelatively higher power density heating element (300) at a tip of theiron compared to the relatively lower power density heating element(301) in the main body of the sole plate. Higher power density may berequired at the tip of the iron particularly where the iron is a steamiron or has a spray which emits water from the front of the iron. Wherethe iron moves in a forward direction and encounters wet or damp cloth,extra energy is required to evaporate moisture or dampness in the clothat the tip of the iron, compared to in the main body of the iron. Whenthe sole plate is moving in a forward direction, the fabric encounteredby the main mid region of the sole plate may be relatively dryer, themoisture having been predominantly evaporated as the tip of the ironmoves over the fabric. If the sole plate had a uniform power densityacross its area, the tip of the iron would become cooler than the mainbody of the iron, since it has more “work” to do, i.e. must dissipatemore energy, because it is the first part of the sole plate whichencounters moist or damp fabric. This can be compensated for byproviding two different power density zones on the iron with a higherpower density heating zone at the tip of the iron compared to theremainder of the sole plate. Since the glass sole plate does not havegood thermal latency, the tip may need to have a higher power densityheating element to give a faster response time to re-heat after ironingdamp fabric.

In FIG. 3 d, each heating zone may be provided with its own temperaturecontrol in the form of its own corresponding respective thermister orother temperature control circuit, so that each of the two heatedregions may have their temperatures maintained substantiallyindependently from each other, subject to thermal transmission throughthe glass or ceramic material of the sole plate between adjacentdifferently heated regions.

The sole plate is not restricted to having two separately temperaturecontrolled and separate temperature heated regions, but rather aplurality of more than two such reasons may be provided on the same soleplate, each having its own corresponding respective heating element andtemperature control circuitry. Each heated region may be provided withits own metallic power rails, for example (302, 303) for the tip region(300), or live and neutral power rails (304, 305) for the central region(301) as shown in FIG. 3 d herein.

Referring to FIG. 4 herein, an alternative scheme is shown. The ATOcoating (or other doped oxide coating) (2) and/or conducting power rails(3, 4) can be configured to maintain a substantially constant powerrating (and therefore heat profile) on an irregularly shaped heating orsole plate of the iron.

As shown in FIG. 4, the ATO coating is patterned into a plurality ofheating elements (2) on the glass sole plate (1). The heating elementsspan between, and are electrically connected to electrically conductingpower rails (3, 4). The conducting power rails (3, 4) provide power tothe plurality of heating elements (2).

In order to achieve a substantially constant power rating (and thereforeheat profile), each of the heating elements (2) are designed to besubstantially the same length. In this embodiment, the heating elementsare shown to turn direction in a zig-zag or serpentine manner betweenthe power rails (3, 4), with the distance between each turn varyingdependent on the position of the individual heating element track on theglass sole plate such that the same track length of heating element isachieved across the whole of the glass sole plate.

Whilst a zig-zag pattern is shown, it would be apparent that othershapes could be considered, with the heating element tracks (2) runningin a length-ways configuration, arcs or other geometric shapes. It isalso envisaged that the patterned heating element track (2) of FIG. 4could be used in conjunction with the patterned metallic tracks forlocalised heating described above and with reference to FIG. 3 forcontrolled heating.

Steam Generator

Referring to FIG. 5 herein, we will now describe a steam generator whichmakes use of a high power density clear thin film resistive coating(ATO) on a glass/ceramic substrate as the heating element to providecompact steam generation. The steam generator may be used in conjunctionwith the iron described above, either integral to the iron, or as astand-alone unit connected to the hub of the iron.

An internal sub assembly of perforated tubes (5) (6) can be rotatedrelative to each other to give a variable fine spray/jet of waterthrough aligned holes (7) directly on the internal surface of an outer(ATO) coated (4) tube heater (1). Steam is created in the internalchamber (8) and forced out under is own pressure through the nozzle (9).Electrical connection to the resistive coating is made via 2 printedsilver contact strips at distal ends of the tube heater (2).

If necessary, a non-return or one way valve can be located at (3) toprevent back pressure into the water reservoir. Under such a scheme itis possible for the mechanism to self pump with an initial primingmechanism.

Alternatively the water would be pumped into the steam generator usingan electrical, manual or heat pump.

Key benefits include the ability to create the steam at source (withinthe iron build) or within a steam generating base/stand and thereforeassist with current issues found in current steam generator productsi.e.:

-   -   Reduced heat up time of initial steam in cold tube set from        generator to iron (at source version)    -   Reduced limescale build up within tube set, since limescale does        not adhere well to either ceramic or glass (at source version)    -   Minimise the size and cumbersome nature of current generators        allowing for more water storage and possible        reconfiguration/appeal of stand unit (Upright docking station,        see through water container, etc)

Another configuration is that this system can be just used as asecondary heat source in the iron component to keep the steam beingdelivered at high temperature on exit.

The coating itself can be used to sense the temperature of the elementand/or the amount of water present in the heater as well as switchingthe heating zones or sections of the element, which we shall nowdescribe.

The steam generator may be provided in a self contained steam iron. Inother embodiments, the steam generator may be located in a steam stationseparate from the hand iron, and the steam is fed to the hand iron via atube.

In a conventional steam iron being supplied with steam from steamstation, the steam passes into a chamber above the soleplate, and heatstored in the metal soleplate serves to reheat any condensate in thesteam received from the steam station. However, if the iron is a glassor ceramic soleplate iron, there is no reheat chamber above thesoleplate, and so a further heater or steam generator may be necessaryin the iron itself as a reheat to remove any condensate in the steamsupplied from the base station. Therefore, in a separate embodimentthere is provided a steam station and station comprising a base stationand a steam iron having a glass soleplate, where the base stationcomprises a steam generator as described in FIG. 5, and the steam ironalso has a steam generator as described in FIG. 5.

Thermal Sensor

Typical thin film coatings are intrinsic semiconductors. For example,SiC and tin oxide are both semiconductors with large band gaps(typically ˜3.2 eV). By doping the semiconductor can be made to ben-type or p-type. Typically, impurities make the thin film an n-typesemiconductor. For example, ATO is an n-type semiconductor. Howeverp-type semiconductors can also be produced.

Typical thin film materials hence have a reversibleresistance—temperature characteristic and thus the heating elementitself can be used as a thermal sensor to measure the temperature of theheating element or substrate. Alternatively, a separate area of thinfilm which does not constitute part of the heating element, but placedon the same substrate close to the element can be used to measure thetemperature using a separate low voltage/low current circuit. The areacan be manufactured using a masking process when the main heatingelement is being created.

It is preferred to detect the resistance change using a low voltage/lowcurrent so that the sensitivity is improved and the semiconductor is notsaturated, hence a separate area for thermal detection is preferredrather than using the bulk element itself. Should the bulk element needto be used, then a high frequency signal multiplexed on to the DC or lowfrequency AC bias can be used to detect variation in resistance, withoutthe requirement to measure high voltages or currents.

The thermal sensor can also be used to detect the temperature of thewater.

Switching Mechanism

In embodiments the heating elements are required to be switched on andoff. This may achieved using a manual switch, a relay or a solid stateswitching device, generally separated from the heating element itself.However this can add extra cost to the overall system.

Hence, it is desired to create a system by which the heating elementswitch is included within the heating element. Given that the thin filmtechnology is a semiconductor, it is possible to create at the same timeas the heating element different types of semiconductor switch orrectifier. In particular, one can produce a FET device by overlaying athin insulator, such as mica or silicon dioxide on top so an area of thethin film element (typically where the current enters or leaves theelement). On top of the insulator a metallisation layer is created towhich a voltage can be applied to switch the element. Further devicesare possible: for example, at the metal—thin film junction a Schottkydiode is created, further using n-type and p-type variants of siliconcarbide or tin oxide it is possible to create a rectifying diode orbipolar transistor. Because the material can withstand hightemperatures, there is no need for a heat sink and any heat losses aredirectly used in the heater, thus increasing efficiency as well asreducing cost. Many of these devices can be transparent and hence can beused within the iron to switch the elements to provide different heatinglevels and control.

In embodiments the element may be switched by TRIAC switching, withdifferential choke filtering (for example, a differential mode filter of18 mH) for EMC capability.

Uniform Heat Distribution

Whilst the serpentine heating element track pattern as shown in FIG. 4herein is aimed at achieving a substantially constant power rating andtherefore heat distribution across the surface of the sole plate, thepattern shown in FIG. 4 is subjected to draw backs.

Firstly, the configuration of FIG. 4 requires a central power rail (4)down a centre line of the sole plate, acting as a live or neutral powersupply line, and first and second peripheral power supply lines, one oneach side of the sole plate. The central power supply track (4) mayinterfere with an even heat distribution down the centre line of thesole plate.

Secondly, the central power supply rail is visually unattractive to theuser, being relatively wider than the serpentine heating elements (2).

Thirdly, the zig-zag or serpentine heating elements extending betweenthe central power rail track (4) and the lateral power rail track (3)are shaped such as to have sharp corners and relatively sharp angles.Sharp corners give rise to high electric field values at the apexes ofthe corners, which can cause hot spots, and reduce reliability.

An alternative arrangement would be to have one power rail (for examplelive) on one side of the sole plate, and another power rail (for exampleneutral) extending along the other opposite side of the sole plate, witha resistive ATO doped semi-conductor film extending across the centre ofthe sole plate between the two power rails.

Referring to FIG. 6 herein, there is illustrated schematically a soleplate comprising a constant thickness doped semi-conductor resistivefilm capable of acting as a heating element between first and secondpower rail tracks (600, 601) respectively one on each side of the soleplate. The doped semi-conductor film is formed on a glass or ceramicsole plate. The arrows shown in FIG. 6 represent current directionbetween the two power rails (600, 601). The power rails (600, 601) areformed of a material which is more conductive than the doped antimonytin oxide resistive film. For example the first and second power rails(600, 601) could be formed from antimony tin oxide which is doped to actas an efficient electrical conductor.

However, using a constant thickness electrically resistive film whichgenerates heat between the two power rails leads to a non-uniform heatdistribution across the sole plate, due to the irregular non-rectangularshape of the sole plate. In particular, as the width of the sole platereduces at the tip (602) and the rear of the sole plate (603), thecurrent density in the ATO film increases relative to its density in thecentre of the sole plate, leading to hot spots at the tip and rear ofthe sole plate relative to the centre of the sole plate. Power densityis proportional to the square of the current density, and so the powerdensity is even less uniform than the current density. The tip of thesole plate and the rear of the sole plate receive much more power thanthe centre of the sole plate and will get much hotter than the centre ofthe sole plate.

Consequently, a uniform resistive thin film between two electrodeseither side of the sole plate would result in an iron having arelatively hot tip and rear, and with the centre of the sole plate beingrelatively cool.

Referring to FIG. 7 herein, one possible solution to the problem of hotspots on the sole plate would be to vary the sheet resistance of the ATOfilm. For example as shown in FIG. 7 herein, the sole plate of the ironcould be divided into a plurality of substantially rectangular ATO filmsections each having a width W across the width of the sole plate, andeach having a height H, being the height of the strip extending betweenthe tip and the rear of the sole plate. Each of the rectangles of ATOthin film has a different sheet resistance. The power density withineach strip of ATO film varies according to the relationship:

$\frac{P}{A} = {\frac{V^{2}}{\sigma_{s}}\frac{1}{W^{2}}}$

However, this approach has the drawback that, for a constant 5.5 W/cm²,the sheet resistance needs to vary enormously in order to give constantpower density, and therefore constant heat distribution within eachstrip. For example, the resistance would need to be 100 Ohms/per square(Ω/sq), for a trip of width 10 cm. For a strip of width 3 cm, the sheetresistance needs to be 1000 Ohms/per square (Ω/sq) and for a strip offilm 1 cm wide, the sheet resistance would need to be 10,000 Ohms/persquare (Ω/sq) in order to achieve a constant power density.

Referring to FIG. 8 herein, there is illustrated schematically a graphof resistive element width in centre metres, against the required sheetresistance in ohms per square to achieve constant power density.

The sheet resistance cannot be varied widely enough to make thisapproach practicable. This approach is unlikely to work because thesheet resistance of the ATO film needs to vary too much (by a factor of100) in order to give a constant power density across a sole plate areahaving curved sides.

Another approach to even out the power density may be to vary the heightof the rectangular strips of thin film heating elements between thefront and the rear of the sole plate.

Referring to FIG. 9 herein, there is illustrated schematically in planview from above, a glass or ceramic sole plate having a plurality of ATOheating elements each extending across the width of the sole plate, eachheating element having a width W and a height h, where each heatingelement is contained within an area of width W and height H. Eachheating element does not necessarily fill the whole of the rectangulararea with dimension W×H.

In this approach, the power density of each heating element isdetermined by the equation

$\frac{P}{A} = {\frac{V^{2}}{\sigma_{s}}\frac{1}{W^{2}}\frac{h}{H}}$

In this case, for a constant power density of 5.5 W/cm², the heatedproportion of each area (h/H) needs to vary widely. For example, for awidth W of 10 cm, the height h of the ATO strip needs to be 100% of theheight of the area H. For a 3 cm wide strip, the height h of the heatingelement needs to be 10% of the height of the rectangular area, and for aheating element 1 cm wide, the height h of the heating element needs tobe 1% of the height H of the rectangular area.

Referring to FIG. 10 herein, there is illustrated a graph of track widthin cm against the proportion of the area heated, for heating elementtrack widths in the range approximately 0.5 cm to 10 cm.

Even if the resistance of the thin film coating is varied as well, thedimensions of the heating element still vary too widely to make thisapproach a practical solution. At the front of the iron, the height ofthe strips would be impractically small, for example 0.1 mm high strips,spaced 1 cm apart.

Referring to FIG. 11 herein, there is illustrated schematically in viewfrom underneath a fifth iron having a transparent or semi-transparentglass or ceramic sole plate, having a fourth heating element tracklayout. The sole plate has formed on it a first ATO power rail track(1101) extending around one side of the sole plate, and a second ATOpower rail track (1102) extending around a second, opposite side of thesole plate. Between the two power rails are positioned a plurality ofthin film semi-conductor resistive heating elements such as antimony tinoxide, fluorine tin oxide or indium tin oxide film resistors. Eachheating element extends between the first power rail and the secondpower rail in a path which veers towards the tip of the front plate,extending from a power rail relatively at the rear of the sole plate,towards a peak position towards the tip of the sole plate, and thenreturning back to join the other opposite power rail towards the rear ofthe sole plate.

In view from underneath, each heating element follows a substantiallypart sinusoidal path between the first and second power rails, whereinan element towards the rear most of the sole plate has a relativelyhighest sine wave spatial frequency, and individual elements towards thecentre of the sole plate, at the position where the sole plate is widesthave a relatively lowest spatial period or frequency. From a position atthe widest point of the sole plate towards the tip, each of the elementshas a successively reduced spatial period towards the tip, the periodfrequency of the substantially sinusoidally shaped elements beingdetermined by the distance between the ends of the element where theymeet the corresponding respective first and second power rails.

The arrangement of elements is designed such that for a constantthickness film and constant width of the element, the shape of theelements, the spacing's between the elements and the positions of theelements relative to each other give rise to a substantially uniformpower density and substantially uniform power dissipation across thesole plate, avoiding localised hot spots. The heating elements have theappearance of a set of ribs running across the area of the sole plate.

At the rear of the sole plate, are provided a pair of contact regions(1104, 1105), for contact of the respective first and second power railsto live and neutral power supplies.

Thermal Fuse

Referring to FIG. 12 herein, there is illustrated schematically in closeup view, a portion of a power rail (1200) of the sole plate of FIG. 12,positioned between a contact pad (1201) for connecting to a liveelectrical power supply, and a plurality of heating elements connectedfurther along the power rail. The power rail section contains a narrowedportion (1202) of relatively reduced track width, the width of the powerrail being selected so as to overheat and evaporate or otherwise burnout, at a pre-determined current density and therefore to self destructas a one time thermal fuse in the event of overheating of the soleplate.

If, for example there is a short circuit between the first and secondpower rails, increased current will flow through the reduced widthsection of the power rail, thereby increasing current density andcausing the reduced section of power rail to “blow” thereby cutting thepower rail. The narrowed fuse section may be doped slightly differentlyto the rest of the power rail, for example with a slightly higherresistance, in order to give it different conductivity properties to thepower rail, in addition to, or instead of having a reduced width.

In other embodiments, instead of or as well as having a reduced width,the thickness of the film may be varied, to a reduced thickness comparedto other parts of the power rail, so that in any event, the fuse sectionof the power rail is electrically and physically the weakest part of thepower rail, and is designed to self destruct as a pre-determined currentflows through the power rail. Once the fuse section is blown, it is notrepairable and the sole plate or iron requires replacement. The fusesection of the thin film power rail is designed to be relatively weaker,having relatively reduced dimensions compared to the rest of the powerrail, and/or having relatively lower conductivity compared to the restof the power rail, so that it acts as the electrically weakest part ofthe power rail.

The embodiments may have a further fuse between the power cable and thecontrols as well as a fuse between the controls and the heating element.

In addition, there may be provided a further mechanical fuse on theheating element side of the controls and switches as well as or insteadof the semiconductor thin film fuse. Thermal fuses may be provided oneach side of the controls.

Iron with Rear Connected Handle and Separate Reservoir

Referring to FIG. 13 herein, there is illustrated schematically inperspective view from one side and above, an eighth iron according to atenth specific embodiment herein. The iron comprises a light weightelectric hand iron component (1300), and a base component (1301) whichalso provides a reservoir for water supply to the hand iron.

The hand iron comprises a substantially transparent sole plate having atransparent or translucent thin film heating element, for example anantimony tin oxide heating element; an upper casing (1302) whichsurrounds a periphery of the sole plate and is positioned on top of theglass or ceramic sole plate, the casing curving up and being formed intoa handle portion (1303) which lies parallel to and above the sole plate,with a gap there between allowing a user to grasp the handle; andpositioned between the glass sole plate and the handle, a transparentupper casing portion (1303) which lies above the glass or ceramic soleplate. The handle is connected to the sole plate and upper casing by arigid rear connecting portion (1304) and there is no connection betweenthe front of the handle and the tip of the upper casing. The uppercasing being transparent, allows the user to see through the casing, andthrough the glass sole plate to see the material being ironed directlyunderneath the glass sole plate. The substantially transparent uppercasing (1303) also provides the function of protecting the users handand fingers from the upper surface of the heated glass sole plate andthermally insulates the user from the heated glass sole plate.

A space or cavity between the convex shaped upper window (1303) and thesubstantially flat planar glass or ceramic sole plate may be filled withan inert or thermally insulating gas, in order to reduce the thermalconductivity between the glass sole plate and the window, or may befilled with air. The cavity may be sealed unit to prevent escape of thegas.

Referring to FIG. 14 herein, there is illustrated schematically thesixth iron and its base in view from above, showing how a user can seethrough the transparent upper cover, through the glass sole plate andunderneath to the base unit. In the iron of FIGS. 13 and 14, water issprayed from a position at the front of the iron, at the front of thehandle, rather than through the glass sole plate. A vapour outlet may beprovided at a front position of the iron, which emits water vapour ormist onto a region immediately in front of the tip of the sole plate. Inthe embodiment shown, the vapour outlet is positioned at the front ofthe handle, overhanging the tip of the sole plate, or alternativelythrough the face of the sole plate.

Referring to FIGS. 15 and 16 herein, there is illustrated schematicallyin cross sectional view, an alternative embodiment sole plate 1500comprising a glass inner plate 1502 and an outer metal e.g. aluminiumrim or frame 1501. The aluminium frame may provide shock resilience ondropping the iron accidentally. Sharp blows to the edge of the soleplate are absorbed by the aluminium edge which extends around aperiphery of the glass sole plate. The glass or ceramic inner sole area1502 is protected from direct impact in a direction along the plane ofthe sole plate, and from impact around the edge of the glass/ceramicportion.

Additionally, the glass/ceramic inner sole area 1502 is slightlyrecessed from the outer metal frame so that if the iron is accidentallydropped so as to land with the sole plate flat or near parallel to thefloor, the inner glass/ceramic sole area 1502 is protected by the outermetal rim. In the best mode, the outer rim may project or protrudebeyond the outer surface of the glass or ceramic portion by a distanceof the order of up to 0.4 mm and preferably 0.2 to 0.3 mm. The exactamount of recess is determined as a trade off between the protecting theglass plate from impact, and the need to have the sole plate in contactwith the surface to be ironed. The inner periphery 1503 of the rim orframe may be chamfered to provide a smooth transition to the glassportion of the sole plate. Other profiles of metal frame are possible,with the effect that a portion of the outer metal frame extending aroundthe glass sole plate extends in a direction perpendicular to the planarsurface of the glass sole portion by an offset distance of the order upto 0.4 mm, and preferably 0.2 to 0.3 mm beyond the outer clothcontacting plane of the glass sole portion.

Referring to FIG. 17 herein, there is illustrated schematically in cutaway view from one side an embodiment glass sole plate iron showing thelayers of construction. A glass sole plate 1700 forms the underside ofthe iron. Spaced apart from and on top of the sole plate is an adjacentsecondary layer 1701, with a gap between the sole plate and thesecondary layer. The secondary layer is preferably transparent or seethrough, but in some embodiments may be opaque.

The secondary layer may form a sealed unit with the sole plate and aninert gas may be contained within the cavity between the sole plate andthe secondary layer. The secondary layer provides thermal insulation andelectrical insulation to the upper side of the sole plate onto which areformed the ATO heating elements 1702.

Over the secondary layer is formed a further cover layer 1703, whichforms the upper part of the case. This layer is preferably transparent,but in some embodiments may be opaque. There is preferably an air gapbetween the upper layer 1703 and the secondary layer. The upper layerprovides an acceptable touch temperature to the user, being thermallyinsulated form the secondary layer and the sole plate by an air gap. Theupper cover layer may be formed of a heat resistant polymer materiale.g. polycarbonate.

In this specification, where resistive heating elements, fuses or othersemi-conductor components have been described utilising antimony tinoxide thin film, such components may be substituted by appropriatelydoped indium tin oxide (ITO) or fluorine tin oxide (FTO) coatings, asare known in the art or mixtures of such oxides.

It will be understood that the invention is not limited to the describedembodiments and encompasses modifications apparent to those skilled inthe art lying within the scope of the claims appended hereto.

1-56. (canceled)
 57. An iron comprising: a sole plate; a secondary layerspaced apart from said sole plate and disposed over said sole plate,said secondary layer being disposed substantially in parallel with saidsole plate, said secondary layer providing electrical and thermalinsulation from said sole plate; and a cavity formed between said soleplate and said secondary layer; said sole plate comprising: a glass orceramic substrate having a glass or ceramic surface for placing incontact with a garment to be ironed; and an electrical heating elementformed as a layer on said glass or ceramic substrate for heating saidglass or ceramic substrate.
 58. The iron according to claim 57, whereinsaid electrical heating element comprises a substantially transparentfilm coating of conducting or semiconducting material.
 59. The ironaccording to claim 57, wherein said electrical heating element comprisesa substantially transparent layer of doped tin oxide.
 60. The iron asclaimed in claim 57, wherein said cavity comprises a sealed cavity whichprovides a thermal and electrical insulation barrier from saidsubstrate.
 61. The iron according to claim 57, further comprising acover layer over said secondary layer, there being an air gap betweensaid cover layer and said secondary layer, wherein said cover layer isthermally insulated from said secondary layer and said sole plate bysaid air gap.
 62. The iron according to claim 57, further comprising acover layer over said secondary layer, there being an air gap betweensaid cover layer and said secondary layer, wherein said cover layer isthermally insulated from said secondary layer and said sole plate bysaid air gap, said cover layer being formed of a heat resistant polymermaterial.